The Birmingham News
Health & Fitness News
By Katherine Bouma, News staff writer
March 22, 2004
When a legislative committee in Montgomery killed a bill banning mercury in dental fillings last month, it didn't determine the safety of the classic silver-colored amalgams that fill the teeth of eight out of 10 Americans.
It will almost certainly be years before that question is answered, as scientists worldwide study the extremely toxic substance that routinely is placed in our mouths to stay for decades. But neither will the controversy abate any time soon.
The bill in the Alabama House of Representatives, which supporters say may come back up this year, would have prohibited dentists from giving children and pregnant women the fillings that still are the No. 1 choice of dentists.
The extreme toxicity of mercury is widely accepted, in fact, has been known for thousands of years. Although amalgam fillings contain about 50 percent mercury, no state has banned their use. The question is whether the small amounts of mercury that leech from them over the years is enough to cause damage.
Mercury exposure can cause serious neurological problems, such as personality change, loss of memory, tremor, lack of coordination, insomnia, fatigue, depression, headaches, irritability, slowed nerve conduction, weight loss, appetite loss, psychological distress and, ultimately, death.
"There's no barrier anywhere in the body, in the sense that the mercury can't get there," said Anne Summers, a professor of microbiology at the University of Georgia.
Across the country, people have testified before their legislatures or other bodies that removing mercury fillings has improved autism, multiple sclerosis, and even infertility, although opponents of the fillings say the links are most often to neurological problems.
Summers said studies have shown that mercury is absorbed by the body in the largest amount when an amalgam filling is put in but continues to leech from the filling forever.
Dentists, who largely oppose bans on amalgam fillings, don't argue that they don't emit mercury forever. They just say it doesn't matter.
"If you use the right instrument, you can detect a small amount of mercury vapor," said Jim Broome, an associate professor at the School of Dentistry at the University of Alabama at Birmingham. "They get a whole lot more mercury out of a can of tuna fish."
The U.S. Food and Drug Administration has reviewed the available studies on amalgams and concluded they are safe to stay on the market, Broome said.
Dentists still overwhelmingly favor the use of the amalgam filling, although its use is dropping as composite materials get better, Broome said. Amalgams last longer, hold better in large cavities, and set more easily and with more disturbances. That's particularly important among children, who often move around or run their tongues over their fillings before they set, Broome said.
"The use of alternative materials has been on the rise," Broome said. "There hasn't been one that totally replaces amalgam. It would be a huge cost to the public."
Anti-mercury activists say the composite fillings wouldn't cost the public much more, although they would cut into dentists' profits, since they take longer to put in place.
Placing mercury directly on humans has been banned in every case that has come up, such as the old disinfectant Mercurochrome, said Charlie Brown, national counsel for the Coalition for Mercury-Free Dentistry.
"Dentistry is the last bastion supporting mercury going into the human body," he said.
Misdiagnosis?:
Broome said that though some people believe amalgams are a problem, the science is not on their side. "There have never been any negative effects to patients or dentists," he said.
Summers said it's impossible to prove such a statement. But it's also difficult, if not impossible, to conduct public health studies of disease outbreaks from mercury. The metal causes a wide variety of symptoms that vary from person to person.
Worse, she said, most of the preliminary symptoms are identical to symptoms of psychological troubles - depression, insomnia, appetite loss and even psychological distress. So a physician could misdiagnose mercury poisoning in early or even later stages, Summers said.
"It's hard to do this science, but it's also important to do this," she said. "We cannot continue to deny this."
In 1992, the Society of Toxicology called for further study into low-level mercury exposure associated with dental amalgams in the areas of neuralgic, reproductive, developmental and renal effects.
By 1997, the National Institutes of Health had begun a 10-year study of amalgam fillings in children. Animal studies have shown that amalgam fillings cause the animals to quickly get high mercury levels in their bodies, Summers said.
She said she is not completely confident the study will show damage, since mercury is a chronic poison that causes damage over 20 or 30 years.
Broome said the study may not show that amalgams are harming children. Results are confidential even from researchers in the midst of such a study, but medical ethics would require the study to be halted if it became clear children were being harmed, Broome said.
"This is not something we take lightly," he said.